Population and urbanisation are increasing with an estimated additional 2.5 billion people living in urban areas by 2050. The built environment is the greatest cause of carbon emissions, global energy demand, resource consumption and waste generation. Therefore, achieving optimal use of space and maximal efficiency in resource use is fundamental if a sustainable tomorrow is to exist. In the built environment there has been a growing belief that taller and denser is better, under the idea that tall buildings make optimal use of space and enable more people per square metre of land to be accommodated. The aim of this research is to investigate which building forms yield maximal efficiency in terms of accommodated population, land use, energy demand, whole-life carbon emissions, and resource consumption. Through case studies and parametric modelling, four realistic urban scenarios have been developed and analysed for WLC: 1) low density, low-rise, 2) low density, high-rise, 3) high density, low-rise, and 4) high density high-rise. These scenarios were then modelled under two conditions; a fixed land area of 1 square kilometre and fixed populations of 20, 30, 40 and 50 thousand people. Key findings from this analysis include that density has no significant impact on WLC while building height significantly impacts WLC. Furthermore, the results show that there is no merit to the claim that building denser and taller urban environments is more sustainable. This multi-criterion approach extends the partial view of most existing research and will enable better-informed decisions for designers, urban planners, and policymakers by providing a more holistic picture of what sustainable urban environments should look like.